package org.nowcoder.leetcode.DP;

/**
 * Title  : 63. Unique Paths II
 * Source : https://leetcode.cn/problems/unique-paths-ii/description/
 * Author : XrazYang
 * Date   : 2023-12-26
 */

public class LeetCode_63 {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        //边界条件
        if (obstacleGrid[0][0] == 1) {
            return 0;
        }

        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;
        //1. dp[i][j] : (0,0) -> (i,j)的路径数
        int[][] dp = new int[m][n];

        //2. 初始状态
        dp[0][0] = 1;
        for (int i = 1; i < n; i++) {
            if (obstacleGrid[0][i] == 1) {
                dp[0][i] = 0;
            } else {
                dp[0][i] = dp[0][i - 1];
            }
        }

        for (int i = 1; i < m; i++) {
            if (obstacleGrid[i][0] == 1) {
                dp[i][0] = 0;
            } else {
                dp[i][0] = dp[i - 1][0];
            }
        }

        //3. 状态转移函数
        for (int i = 1; i < m; i++) {
            for (int j = 1; j < n; j++) {
                if (obstacleGrid[i][j] == 1) {
                    dp[i][j] = 0;
                } else {
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        return dp[m - 1][n - 1];
    }
}
